If you're a member of the #silvergoldstackers community, and you post about precious metals, and you use the tag #silvergoldstackers, then the bot will upvote your post.

If you're NOT a member of the community, the bot will not upvote you regardless of what tag or post you use.

In essence, only members posts, using the correct tag, which is actually about PMs will get an upvote.